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• Leukocytes (white blood cells) are crucial for immunity
• Leukocytes


  White blood cells involved in the immune response
• Types of leukocytes

  • Granulocytes
  • Agranulocytes
• Types of granulocytes

  • Neutrophils
  • Eosinophils
  • Basophils
• Types of agranulocytes

  • Lymphocytes (B cells and T cells)
  • Monocytes (macrophages)
• Function of neutrophils, eosinophils, basophils

  • Part of innate immunity
• Function of lymphocytes (B cells and T cells)

  • Part of adaptive immunity
• Function of monocytes (macrophages)

  • Act as non-specific cleaners, remove debris and pathogens
• Immune organs

  • Lymph nodes
  • Bone marrow
  • Thymus
  • Spleen
• Lymph nodes

  Filter lymph and help fight bacteria/viruses
• Bone marrow

  Produces immune cells
• Thymus

  Secretes thymosin to stimulate maturation of T cells
• Spleen

  Stores blood and filters both blood and lymph
• Nonspecific immune response

  Response without prior learning, general defense mechanisms
• Adaptive immunity

  Specific immune response developed through learning to recognize specific antigens
• Parts of adaptive immunity

  • Humoral immunity
  • Cell-mediated immunity
• Humoral immunity

  Driven by B cells and antibodies
• Cell-mediated immunity

  Provided by T cells
• Autoimmunity occurs when the immune system attacks self-antigens, mistaking them for foreign
• Autoimmune diseases

  • Rheumatoid arthritis
  • Lupus
• Hypersensitivity reactions occur when the immune system overreacts to harmless antigens
• Nonspecific defense mechanisms

  • Skin
  • Respiratory system
  • Macrophages and granulocytes
  • Interferon
• Skin

  • Acts as a physical barrier to prevent microbes from entering, sweat contains enzymes that destroy bacterial cell walls
• Respiratory system

  • Mucous membranes lined with cilia trap bacteria/viruses, produce enzymes that kill bacteria
• Macrophages and granulocytes

  • Destroy pathogens when they get past skin, histamine helps these cells move from bloodstream to fight infections
• Interferon

  Protein that stops viruses from replicating and spreading
• Humoral immunity takes a few days for the body to recover when encountering a pathogen
• Antibodies (immunoglobulins)

  • Bind to specific parts of pathogens called antigens, attract other immune cells or clump together pathogens to eat
• Antibodies structure

  Y shaped molecules with heavy chains and light chains bound by strong bonds
• Each B cell makes a unique antibody
• Not all B cells produce antibodies all the time because making antibodies uses a lot of energy
• B cells wait in lymph nodes

  • Until they find their specific antigen
• B cell response to antigen

  1. Find antigen

  2. Make plasma cells

  3. Produce antibodies

  4. Make memory cells
• Plasma cells


  • Produce lots of antibodies and eventually die
• Memory cells

  • Stay in lymph nodes for future use and last a long time
• Vaccinations help the body make memory cells
• Memory cells allow for a faster and stronger response without causing illness
• T cells

  • Involved in cell-mediated immunity, originate from bone marrow stem cells but mature in thymus
• Types of T cells

  • Helper T cells
  • Cytotoxic T cells
  • Memory T cells
• Helper T cells

  • Express CD4 protein, coordinate immune response by secreting lymphokines, recruit/activate other immune cells